Both reverse osmosis and forward osmosis have been used for water treatment.
Reverse osmosis is a pressure-driven process, requiring a high pressure exerted on a membrane. To withstand a pressure as high as 1200 psi, a reverse osmosis membrane has a dense layer of polymer matrix, which often causes fouling.
Forward osmosis, by contrast, is a process driven by diffusion instead of pressure. In a forward osmosis process, a solution of a considerably high concentration, i.e., draw solution, is utilized to generate a hydrostatic osmotic pressure gradient across a membrane to extract fresh water from a feed solution (such as seawater, brine, or any waste water) on the other side of the membrane. Since this process capitalizes natural osmosis, little energy is required.
Commercially available forward osmosis membranes, typically made of cellulose-based polymers, have unsatisfactory durability and performances. There is a need to develop a durable and highly efficient forward osmosis membrane.